1. Field of the Invention
The present invention relates to an ink-jet recording ink set, a recording head, an ink-jet recording apparatus, and an ink-jet recording method.
2. Description of the Related Art
An ink-jet recording method is a recording method for forming an image by causing a small-size ink droplet ejected from a recording head to fly onto plain paper or a dedicated glossy medium. Because a recording apparatus has become less expensive and improved in recording speed, the above-mentioned recording method has rapidly enhanced its popularity in recent years. Further, because the image quality has become higher in the recording method to enable output of a photographic image comparable to a silver-halide photograph, and because a digital camera has rapidly enhanced its popularity, the above-mentioned recording method has become more popular also as a method of outputting a photographic image.
In recent years, a technology such as an extreme reduction in size of an ink droplet to be flown or the expansion of a color gamut in association with the introduction of a multi-color ink has been introduced into the recording method, and hence an additional improvement in image quality has been progressing. Therefore, a coloring material, in particular, a dye has been required to achieve higher levels of color developability and fastness properties (such as light resistance and ozone resistance) of an image than conventional ones.
For example, an azo dyestuff having a specific dyestuff skeleton has been proposed as a dye having high fastness properties against light and ozone (Japanese Patent Application Laid-Open No. 2006-143989). Japanese Patent Application Laid-Open No. 2006-143989 describes that the azo dyestuff has sufficient fastness properties against light, heat, humidity, and an active gas in an environment.
In addition, a dye for a magenta ink having a specific molecular structure has been proposed (Japanese Patent Application Laid-Open No. 2012-25156). Japanese Patent Application Laid-Open No. 2012-25156 describes that the dye has high fixability to the ink-receiving layer of a recording medium and improves the fastness properties of an image such as bronze resistance.
The dye described in Japanese Patent Application Laid-Open No. 2006-143989 or Japanese Patent Application Laid-Open No. 2012-25156 has an advantage in that the dye is excellent in fastness properties against light and ozone. However, when an ink set is constituted by combining an ink containing the dye and an ink containing any other dye, a problem arises in that the ink containing the dye cannot obtain an ejection characteristic comparable to that of the ink containing the other dye. As a result, a problem arises in that the respective inks of the ink set are not uniformly ejected and hence the printing quality of an image reduces.
The problem arises probably because the dye is designed to have such a molecular structure that dye molecules easily associate with each other, i.e., a molecular structure having high hydrophobicity in order that its fastness properties against light and ozone may be improved. That is, the ink containing the dye having high hydrophobicity and an ink containing an ordinary hydrophilic dye have different properties, and hence a difference is assumed to occur between the ejection characteristics of the inks even when the inks have the same ink composition.
In particular, the miniaturization of an ink ejection orifice has been progressing in a recent ink-jet recording apparatus in association with an improvement in quality of an image. In addition, a recording head in which an ejection condition is strict and ejection stability is hard to secure like a line-type head or a gas-liquid separation-type recording head has started to appear. Therefore, the problem may become additionally serious.